When the astronauts go into space with a space shuttle. They go at very high speeds and I was wondering if they blackout when entering or exiting the atmoshpere or even before that. And how many g's is it at top velocity.

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perfect is an opinion word-3dknight

it doesn't matter if I get 3 hours of sleep or 6, I still wake up just as tired!-Neverfly

These are the questions that boggle my mind-3dknight

The space shuttle only pulls a little more than 3.0gs and that right before main engine cutoff. Most of the pilots are military pilots so they have experience with those kinds of forces.

But if you take a Russian capsule back you might get up to nearly 10 g!! Yikes...

So could a person passout in a russian capsule??? Perhaps a regular citizen with no experience to these forces.

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perfect is an opinion word-3dknight

it doesn't matter if I get 3 hours of sleep or 6, I still wake up just as tired!-Neverfly

These are the questions that boggle my mind-3dknight

Sometimes they black out during the welcome-home ceremony.

ABC News: Space Travel Can Be a Trying on the Body

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On rough re-entries (of which the Soyuz has had its fair share, and to its credit usually survived) it can happen and it has happened.

A normal Soyuz re-entry, IIRC is in the region 7-8g which is a lot, but if you pass out at that point you probably aren't going to be allowed on a Soyuz.

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"I worry that, especially as the Millennium edges nearer, pseudo-science and superstition will seem year by year more tempting, the siren song of unreason more sonorous and attractive." - Carl Sagan, 1995

Just as a point of clarification, the g's don't depend on the velocity, but rather on the acceleration. Just think of a car. When you hit the accelerator hard, or hit the brake hard, you will feel g's. But even if you're going at top speed, you won't be pushed into the seat, because you're not speeding up or slowing down. For the space shuttle, the top velocity is generally speaking the whole time they are floating (in almost zero g) in orbit. But the highest g's are either when they hit the atmosphere or when they are about to dump the solid rocket boosters (because they have burnt up a lot of fuel, and the whole thing is lighter, making acceleration higher).

And the reason they black out during ceremonies and not in the ship is that even though it may be 4 g's, they are lying down on their backs. The reason you black out during high g's is because the blood either leaves your head. So lying on your back makes it much harder to black out.

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As above, so below

And hydrating, and g-suits and training and, potentially, drugs.

Science@NASA: When Space Makes You Dizzy

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Well on the Soyouz T10-1 the rocket had a major malfunction on the launch pad and the crew survived only because of the escape system. "the escape system motor fired, dragging the orbital module and descent module, encased within the upper shroud, free of the booster with an acceleration of 14 to 17g (137 to 167 m/s²) for five seconds."

Can't have been a pleasant ride, but when you escape alive it's all good

Visual enjoyment can be had here http://www.youtube.com/watch?v=UyFF4cpMVag

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The impossible often has a kind of integrity which the merely improbable lacks.

I didn't know there was video of that event!

IIRC, they were unconscious and overall a bit wrinkly after that flight, but indeed they all survived without major injuries.

IIRC² the escape system had to be activated from the control room, not from the capsule itself. And IIRC³ there was a problem with the wire sending this message already being burnt through, so they had to switch to a radio system. That's why it took so long to launch them clear from the pad. If the communication with wire had worked, they would have evacuated much sooner. it was clear this was not going to be a mission from the start of the fire .

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To the regular visitor of internet bulletin boards it is clear that it's an excellent idea your parents get to choose your real name.

At 10 Gs, yes, but only if they were sitting up. In the Russion capsules they're reclining, so the blood doesn't rush from one's head. 10 Gs while reclining is probably similar to 2 Gs sitting up, or 1.5 Gs standing up. I've taken 3 Gs for more than a minute standing up, and 6 Gs for more than a minute sitting down, both without a G-suit.

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I am Mugs, of the Alien clan of Usa, Nordamerica, a Terran, of Sol.

Mine: "Perception isn't reality. It's merely an abstraction thereof, and quite often not a very good one at that."

Heinlein's: "Staying young requires the unceasing cultivation of the ability to unlearn old falsehoods." "Freedom begins when you tell Ms. Grundy to go fly a kite."

Let's not give the impression that six Gs is routine. Without any experience or warning, you could hurt yourself and you will have problems breathing normally.

Now, 6 Gs while floating in water, that's what I'm talking about.

The Carnival came to town recently, April 19th in fact, and they had that spinning room that pushes on the g's. It was a lot of fun. Lifting my arm was easy, but I couldn't lift my body up. And yes, I am quite weak. Still, it would be a lot of fun to own one of those centrifuges.

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It's not the breathing that's an issue. It's the blood rushing from your head into your lower extremities and leaving your brain without oxygen.

And yes, floating in water you could easily withstand 50 G's.

As for the carnival rides, they're usually designed for people in a prone (on their back) position at around 4 G's.

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I am Mugs, of the Alien clan of Usa, Nordamerica, a Terran, of Sol.

Mine: "Perception isn't reality. It's merely an abstraction thereof, and quite often not a very good one at that."

Heinlein's: "Staying young requires the unceasing cultivation of the ability to unlearn old falsehoods." "Freedom begins when you tell Ms. Grundy to go fly a kite."

I guess that for carnival rides, the issue is not whether people will black out, but rather whether they will injure their lower backs or necks and sue the operator.

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As above, so below

I recall that nearly all such rides have disclaimer signs something along the lines of "do not ride if you have any physical disability or history of heart disease, are at risk for stroke," etc.

Plus, partof the rider operator's duties is to screen people, and they also have posted "the ride operation retains the authority to refuse anyone entrance to this attraction at any time."

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I am Mugs, of the Alien clan of Usa, Nordamerica, a Terran, of Sol.

Mine: "Perception isn't reality. It's merely an abstraction thereof, and quite often not a very good one at that."

Heinlein's: "Staying young requires the unceasing cultivation of the ability to unlearn old falsehoods." "Freedom begins when you tell Ms. Grundy to go fly a kite."

IIRC, lying flat on your back allows you to stand quite high g forces, once, but after that, less and less each time. Is that true, and if so, why?

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IIRC, lying flat on your back allows you to stand quite high g forces, once, but after that, less and less each time. Is that true, and if so, why?

I know of nothing that indicates G tolerance decreases after each exposure. Fighter pilots may fly for 20 years or more (with the occassional desk job for "career broadening") and they're exposed to high Gs everytime they do dogfight training (without the benefit of lying flat). There are aging factors to consider but not exposure factors. Likewise, the Mercury and Gemini astronauts were launched by converted ICBMs and pulled a lot of Gs. I've read that Gemini astronauts pulled over 7 Gs during launch and even more during reentry. Several of the early astronauts flew more than once.

Somewhat ghoulish SF reference. In Alastair Reynolds' "Absolution Gap" a spacecraft responds to an emergency beacon. The spacecraft has safeguards to prevent it from killing its passengers through excessive G forces, but it happens to be unaware that it has a passenger. The ship reaches distress signal at maximum speed, and when the person rescued opens up the passenger's spacesuit, he finds bloody pulp full of broken bones. What kind of acceleration THAT would take? I estimate about 100 g, before ribs break under their own weight.

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Fiction has to be plausible. Reality is under no such constraint.

You're absolutely correct, Larry Jacks. In fact, frequent and repeated exposure only strengthens the muscles used in the M-1 maneuver (rapid and progressive tensing of muscles from the foot up through the abdomen to counteract the tendancy of one's blood under high G to move and pool downward.

It's usually after those "career broadening" tours of duty that their resistance to G forces has been diminished due to lack of practice.

7 Gs lying down is nothing. Sitting in a chair it's nearly impossible to maintain consciousness for more than a minute, ev